Method of making a smokable product from oxidized cellulose

ABSTRACT

A method for preparing a smokable product wherein a cellulosic material is first selectively oxidized with a gaseous nitrogen dioxide, and the resulting oxidized cellulosic material is thereafter subjected to a reduction reaction by means of a borohydride at an alkaline pH.

United States Patent Briskin et al.

[451 Feb. 22, 1972 [54] METHOD OF MAKING A SMOKABLE PRODUCT FROM OXIDIZED CELLULOSE [72] inventors: Theodore S. Brlskln, Beverly Hills; Allen 11. Remanlck, Pasadena, both of Calif.

[73] Assignee: Sutton Research Corporation, Los Angeles, Calif.

[22] Filed: Jan. 22, 1970 [21] App1.No.: 5,098

[52] U.S.Cl ..l31/2, 131/17 [51] Int. Cl. ..A24d 01/18 [58] FieldoiSearch ..l3l/2, 17, 140-144 [56] References Cited UNITED STATES PATENTS 3,478,751 11/1969 Briskin et a1 ..131/2 3,447,539 6/1969 Briskin et 211... 3,007,917 11/1961 Pauling ..l3l/2 UX Primary Examiner- Melvin D. Rein Attorney-McDougal1, Hersh & Scott [57] ABSTRACT 14 Claims, No Drawings METHOD OF MAKING A SMOKABLE PRODUCT FROM OXIDIZED CELLULOSE This invention relates to new smoking products and to a method for preparing them.

As used herein, the term smoking products is meant to refer to and to include filler material embodied in cigarette, cigars and for use with pipes and the like, and mixtures thereof with various proportions of tobacco and including cigarette papers and wrappers used in the preparation of such cigars and cigarettes, and it includes cigarettes, cigars and the like products manufactured with such filler materials and wrappers.

In U.S. Pat. No. 3,447,539 and copending applications, Ser. Nos. 674,994 now abandoned and 802,229, description is made of the preparation of a smoking product suitable for use in cigarettes, cigars or with pipes wherein the smoking product is prepared of relatively pure cellulosic materials subjected to selective oxidation with liquid nitrogen dioxide to convert preferably more than 90 percent of the methylol groups in the cellulosic molecule to yield a product which can be referred to as an oxycellulose or polyuronic acid. The oxidation reaction product is further processed by removal of liquid nitrogen dioxide by vaporization and preferably by washing the oxidized cellulosic product with water and/or alcohol and/or acetone or other solvent for removal of solubilized foreign material, including oils, waxes, latices and the like, which contribute undesirably to the taste and aroma when used as a smoking product in accordance with the practice of this invention.

In US. Pat. No. 3,478,751, description is made ofa method for treating an oxidized cellulosic material to provide a smoking product having improved characteristics from the standpoint of odor and mildness wherein an oxidized cellulosic material is treated with a borohydride or hydrogen gas to effcct reduction of various nitric acid esters and/or nitro groups as well as to effect reduction of quinones, ketones and aldehydes which are present in the oxidized cellulosic material and which undesirably contribute to the taste and odor of the resulting product when used as a smoking product.

The resulting smoking product can then be formulated with mineralizing agents, such as oxalates, citrates, glycolates, diglycolates, lactates, pivalates or tannates of such metals as calcium, magnesium, lithium, potassium, barium, strontium, preferably introduced to form the salt internally in the cellulosic derivative for purposes of providing desired ashing characteristics, Instead of forming the described salts internally in the cellulosic derivative, limited beneficial characteristics can be achieved by external application of such mineralizing agents. As described, the desiredinternal introduction is achieved by first wetting the cellulosic derivative with metal cation in dilute solution for absorption into the cellulosic derivative followed by exposure to the acid anion in solution to precipitate the metal salt in situ in the cellulosic material.

The oxidized cellulosic material treated in accordance with the method described in the aforementioned patent is preferably prepared by selective oxidation of a cellulosic material with liquid nitrogen dioxide. For example, one method for effecting this oxidation'is disclosed in copending application, Ser. No. 745,221, filed July 16, 1968, wherein description is made of the oxidation of a cellulosic material by suspension in liquid nitrogen dioxide in the ratio of 1 part by weight cellulosic material to 5 to 1,000 parts by weight liquid nitrogen dioxide, and preferably 1 part by weight cellulosic material to 25 to 50 parts by weight of the liquid nitrogen dioxide. The reaction therein is carried out at a temperature within the range of to 65 C., and at autogenous pressure when the reaction temperature exceeds 21 C., the boiling point of nitrogen dioxide.

Another method for effecting their oxidation is described in copending application, Ser. No. 745,135, entitled Preparation of Smoking Products of Cellulose Derivatives and Process," filed July 16, 1968, wherein the oxidation reaction, including reaction rate and amount of conversion, is materially improved by formulation of the oxidation reaction mixture to contain up to 8 percent by weight of water in the liquid nitrogen dioxide system and by carrying out the reaction at elevated temperatures above 15 C., and preferably between the range of 20 to 45 C., depending somewhat upon the amount of moisture present in the reaction medium, whereby the reaction medium is rendered relatively nonelectrically conductive so that the presence of water in the reaction medium will not result in attack or degradation of the cellulosic material to be oxidized, and wherein the formulation to include aqueous medium in the reaction of liquid nitrogen dioxide also operates to adjust the specific gravity of the reaction mixture in the direction towards the specific gravity of the cellulosic material whereby suspension of the cellulosic material in the reaction medium is easier to achieve and maintain. The result is a more rapid and uniform oxidation reaction of the cellulosic material to produce a better product at a more rapid rate.

It is an object of the present invention to provide a new and improved smoking product and method for its preparation which is suitable for use in smoking and which finds wide acceptance as a smoking product from the standpoint of taste, aroma and mildness.

The concepts of the present invention reside in a method for preparing a new and improved smoking product wherein a cellulosic material is first selectively oxidized by means of gaseous nitrogen dioxide to provide an oxidized cellulosic material, which is then treated with a borohydride to effect reduction of various nitric acid esters and/or nitro groups as well as quinones, ketones and aldehydes which are present in the cellulose molecule and/or as impurities in the oxidized cellulose.

It has been found that cellulosic materials treated in this manner are particularly well suited for use as smoking products which are pleasing to the user from the standpoint of taste, aroma and mildness. In addition, the new and improved smoking products of the present invention may be efficiently produced by a method characterized by a high reaction rate in the oxidation reaction, and a complete reduction reaction which is effective to substantially completely reduce quinone, ketone and aldehyde groups which contribute undesirable components to the smokeof smoking products to provide an oxidized cellulose having significantly improved stability.

As the cellulosic raw material, use can be made of various forms of cellulose, such as wood pulp, straw, alphacellulose, flax, fibrous carbohydrates, seaweed carbohydrates, bamboo filaments, cotton filaments, hemp, refined paper, rice paper, filamentous gumsand even plants and plant leaves and the like fibrous materials from which noncarbohydrate components have been separated, all of which is hereinafter referred to as cellulosic material.

It is preferred to make use of a purified cellulosic material from which various of the sugars, proteins, chlorophylls, flavones, colors, lignins, oils, waxes, resins and lactices have been removed since these contribute undesirable odors and tastes to the smoking product.

In carrying out the oxidation reaction with gaseous nitrogen dioxide, the cellulosic material can be contacted with gaseous nitrogen dioxide, or a mixture of nitrogen dioxide and nitric oxide, at a temperature within the range of 25-225 C. for a period of up to 40 hours to convert at least percent of the methyol groups in the cellulose molecule. The reaction pressure is not critical and can be varied within wide ranges, such as from 0.5 to 3 atmosphere guage.

If desired, the rate of reaction using gaseous nitrogen dioxide can be increased by the presence of moisture in the cellulosic material to be oxidized. For example, the rate of reaction of a cellulosic material which contains about 8 percent moisture by weight is about twice the rate of a cellulosic material containing substantially no moisture. Thus, it is frequently desirable to wet the cellulosic raw material prior to contacting it with gaseous nitrogen dioxide to provide a moisture level in the cellulosic material of up to about 10 percent by weight. Since the gaseous nitrogen dioxide has the effect of drying out the cellulosic material with which it is reacted, it is also possible, and frequently desirable, to'repeat the sequence of wetting the cellulosic raw material with water to provide the desired moisture content and the exposing it to gaseous nitrogen dioxide several times until the desired level of oxidation has been achieved.

One of the difficulties experienced in the use of gaseous nitrogen dioxide is the rapid release of the heat of absorption and the heat of reaction liberated by the exothermicreaction which occurs when the cellulosic material is first exposed to gaseous nitrogen dioxide. This rapid release of heat canhave a deleterious effect upon the cellulosic material in that it tends to cause thermal degradation of the cellulosic material. In order to minimize the adverse effects of the highly exothermic oxidation reaction, it is frequently preferred to effect the oxidation in accordance with the method described in copending application, Ser. No. 774,064, filed Nov. 7, 1968, and entitled Method for Producing Smoking Product of Oxidized Cellulosic Material.

The method as described in the aforementioned application includes the sequence of wetting the cellulosic material with liquid nitrogen dioxide and then exposing the cellulosic material to gaseous nitrogen dioxide to effect the oxidation reaction in order to facilitate a rapid rate of reaction, the liquid nitrogen dioxide which is used to wet the cellulosic material prior to exposure to gaseous nitrogen dioxide may optionally contain up to about 10 percent by weight water which serves to maintain the moisture content of the cellulosic material undergoing oxidation. It is generally desirable to repeat the sequence of wetting the cellulosic material with liquid nitrogen dioxide and then exposing it to gaseous nitrogen dioxide until the desired conversion of the methylol groups in the cellulose molecule has been achieved.

The temperatures and pressures used in effecting the oxidation are not critical and can be varied within wide ranges. It is generally preferred to employ a temperature within the range of 25 to 225 C. and a pressure within the range of 0.5 to 3 atmospheres.

After oxidation with gaseous nitrogen dioxide, the oxidized cellulosic material is subjected to a reduction reaction with a borohydride. As the borohydride, use can be made of the alkali metal borohydrides, such as sodium borohydride, potassium borohydride, lithium borohydride, etc., the alkaline earth metal borohydrides, such as calcium borohydride, magnesium borohydride, etc., or ammonium borohydride. The preferred borohydrides are the alkali metal borohydrides.

The reduction using one or more of the above borohydrides may be effected in a variety of ways. For example, as described in US. Pat. No. 3,478,751, the borohydride reduction may carried out in aqueous medium having a pH below 7 but not below 3, and preferably a pH within the range of to 6.5. Adjustment of the pH to the desired level can conveniently be achieved by means of the addition of an organic acid to the aqueous reaction mixture, such as oxalic acid, acetic acid, glucuronic acid, oxidized cellulose or similar organic acids, or by the addition of an inorganic acid, such as hydrochloric acid, nitric acid or the like. It is preferred to make use of an organic acid, and particularly oxalic acid, because the use of inorganic acid necessitates the use of subsequent treating steps to remove inorganic acid ions, such as the chloride ion. Oxalic acid which might remain in the treated oxidized cellulosic material after the reduction reaction need not be removed since beneficial use can be made of the oxalic acid present in producing oxalates for mineralizing and for providing the desired ashing characteristics in the resulting oxidized cellulose smoking product.

When using the above-described conditions, the reaction can be carried out at a temperature within the range of 0 to 30 C., and preferably within the range of 0 to 25 C. for a period of 1 minute to 2 hours and preferably -30 minutes. The amount of borohydride used is preferably l-100 parts by weight of the borohydride per 1,000 parts by weight of the oxidized cellulosic material.

As indicated, the borohydride treatment described in the aforementioned patent contemplates a reduction reaction carried out at an acidic pH in order to minimize dissolution of the oxidized cellulosic material in the aqueous media. It has now been found that reduction with one or more of the above borohydrides can be achieved by reacting the borohydride with an oxidized cellulose at an alkaline pH. The reaction can be carried out by dispersing the oxidized cellulose in water or aqueous alcohol, adding a base to raise the pH to at least 8.5, and preferably to a pH within the range of 9 to l2, and then adding the borohydride in an amount described above. The reaction can be allowed to proceed at a temperature within the range of 0 to 70 C., and preferably 0 to 30 C., for a period of 1 minute to 5 hours.

The relative absence of dissolution of the cellulosic material in the alkaline media is believed to be due at least in part to the reaction medium in the form of a water-alcohol mixture and careful choice of base. For this purpose, use can be made of a reaction medium comprising at least 20 percent by weight ofa lower alkanol containing one to five carbon atoms such as methanol, ethanol, isopropanol, etc., and preferably a solution of 50-85 percent by weight of the alkanol. The reaction medium can be rendered alkaline by the addition thereto of a base, such as an alkali metal bicarbonate or hydroxide, or an alkaline earth metal hydroxide.

This particular method of effecting the reduction of an oxidized cellulosic material which has been prepared by selective oxidation using gaseous nitrogen dioxide has been found to produce an oxidized cellulosic material which is particularly stable against the effects of aging and the like and which provides a smoke with a particularly mile taste and aroma.

Having described the basic concepts of the invention, reference is now made to the following examples, which are provided by way of illustration and not by way of limitation, of the practice of the present invention.

EXAMPLE 1 Purified cellulose paper in the form of strips is moistened with water to provide a moisture content of 1.7 percent by weight, and then is contacted with hot gaseous nitrogen diox ide maintained at a temperature of 70 C. and atmospheric pressure. A rapid reaction occurs, but tapers off within about 8 minutes to provide an oxidation level of 18 percent of the methylol groups in the cellulose molecule.

Thereafter, theeycle is repeated until at least percent of the methylol groups have been converted. After removal of thenitrogen dioxide and washing of the oxidized cellulose, it is placed into a suspension of calcium carbonate and treated with limewater to raise the pH to 9.5. A quantity of sodium borohydride is added so as to provide a ratio of 1 part of borohydride to 10 parts of oxidized cellulose.

The reaction is allowed to proceed at room temperature for 25 minutes. The liquid is drained from the cellulosic material which is then washed several times with dilute oxalic acid. This serves to remove ions such as sodium and borate and to incorporate the calcium as calcium oxalate for a mineralizing agent. Residual oxalic acid is removed by washing the product with water.

The resulting product can be, if desired, further processed to introduce burning control agents, such as potassium, rubidium or cesium salts (e.g., oxalates), as described in the abovementioned patents.

EXAMPLE 2 Purified cellulose strips of the type used in Example 1 are placed in a close reactor which is then evacuated. The reactor is filled with a mixture comprising 8 mole percent nitric oxide and 92 mole percent nitrogen dioxide, The mixture is allowed to react for 48 hours. An oxidation level of greater than 80 percent is achieved.

After removal of the nitrogen oxides by evacuation, the oxidized cellulose is washed and placed in a suspension of calcium citrate. Limewater is added until the pH is 11.0. Most of the residual solution is drained. To the resulting suspension is added a quantity of sodium borohydride corresponding to 3 parts of sodium borohydride per lOO parts of oxidized cellulose. After minutes reaction, the liquid is drained and washed several times with citric acid and saturated calcium citrate. Other organic acids and their corresponding calcium and/or magnesium salts may be used to incorporate desired mineralizing component.

EXAMPLE 3 The purified cellulose paper used in Example l is dipped in liquid nitrogen dioxide containing 1 percent by weight water. While the ccllulosic material is still wet with the liquid nitrogen dioxide, it is contacted with gaseous nitrogen dioxide at 80 C. After 8 minutes, the reaction begins to subside and the oxidation level is determined to be about 42 percent. The

cycle is repeated when the oxidation level is at least 80 percent, and the oxidized cellulose is washed.

Thereafter, the oxidized cellulose is placed in a mixture of 70 percent by weight methanol and percent by weight water, and a solution of 0.5 N NaOH is added in an amount sufficient to raise the pH of the mixture to about l0.5. Then sodium borohydride is added to provide a ratio of 0.1 part by weight borohydride per 1 part by weight oxidized cellulose. The mixture is stirred for about 30 minutes at room temperature, after which the ccllulosic material is removed, washed with dilute HCl, washed with water and dried.

The oxidized cellulose which has been treated in the above manner is preferably further processed to include a mineralizing agent and/or a burn control agent in order to further enhance its characteristics as a smoking product in the manner described in the aforementioned patents and applications.

It will be apparent from the foregoing that we have provided a new and improved method for preparing a smokable product which is characterized by a heretofore unknown efficiency in that the use of liquid nitrogen dioxide as the primary oxidation agent can be completely avoided. In addition, the method of the present invention provides a smokable product having improved stability over products heretofore prepared.

it will be understood that various changes and modifications may be made in the details of formulation, procedure and use without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. A method for preparing a smokable product comprising the steps of selectively oxidizing a ccllulosic material with gaseous nitrogen dioxide and then subjecting the oxidized cellulosic material to a reduction reaction with a borohydride at an alkaline pH.

2. A method as defined in claim 1 wherein said gaseous nitrogen dioxide includes nitric oxide.

3. A method as defined in claim 1 wherein the oxidation reaction is carried out at a temperature of 25 to 225 C.

4. A method as defined in claim 1 wherein said ccllulosic material contains up to about 10 percent by weight moisture.

5. A method as defined in claim 1 which includes the step of adding water to said cellulosic material prior to the oxidation reaction to provide a moisture content of up to 10 percent by weight.

6. A method as defined in claim 1 which includes the sequence of wetting the cellulosic material with water to provide a moisture content of up to 10 percent by weight and then contacting the wetted ccllulosic material with gaseous nitrogen dioxide.

7. A method as defined in claim 6 wherein said sequence is repeated until at least percent of the methylol groups in the cellulose molecule have been converted.

8. A method as defined in claim 1 which includes the step of wetting the ccllulosic material with liquid nitrogen dioxide prior to reaction with aseousnitrogen dioxide. I t I 9. A method as efined in claim 8 wherem said liquid nitrogen dioxide contains up to 80 percent by weight water.

9. A method as defined in claim 1 which includes the sequence of first wetting the cellulosic material with liquid nitrogen dioxide and then exposing the ccllulosic material to gaseous nitrogen dioxide and repeating the sequence until at least 80 percent of the methylol groups in the cellulose molecule have been converted.

11. A method as defined in claim 1 wherein the reduction is carried out in an alcohol water mixture.

12. A method as defined in claim 11 wherein said mixture comprises at least 20 percent by weight alcohol.

13. A method as defined in claim 11 wherein said mixture comprises between 50 and percent by weight alcohol.

14. A method as defined in claim 11 wherein said alcohol is a lower alkanol. 

2. A method as defined in claim 1 wherein said gaseous nitrogen dioxide includes nitric oxide.
 3. A method as defined in claim 1 wherein the oxidation reaction is carried out at a temperature of 25* to 225* C.
 4. A method as defined in claim 1 wherein said cellulosic material contains up to about 10 percent by weight moisture.
 5. A method as defined in claim 1 which includes the step of adding water to said cellulosic material prior to the oxidation reaction to provide a moisture content of up to 10 percent by weight.
 6. A method as defined in claim 1 which includes the sequence of wetting the cellulosic material with water to provide a moisture content of up to 10 percent by weight and then contacting the wetted cellulosic material with gaseous nitrogen dioxide.
 7. A method as defined in claim 6 wherein said sequence is repeated until at least 80 percent of the methylol groups in the cellulose molecule have been converted.
 8. A method as defined in claim 1 which includes the step of wetting the cellulosic material with liquid nitrogen dioxide prior to reaction with gaseous nitrogen dioxide.
 9. A method as defined in claim 8 wherein said liquid nitrogen dioxide contains up to 80 percent by weight water.
 9. A method as defined in claim 1 which includes the sequence of first wetting the cellulosic material with liquid nitrogen dioxide and then exposing the cellulosic material to gaseous nitrogen dioxide and repeating the sequence until at least 80 percent of the methylol groups in the cellulose molecule have been converted.
 11. A method as defined in claim 1 wherein the reduction is carried out in an alcohol water mixture.
 12. A method as defined in claim 11 wherein said mixture comprises at least 20 percent by weight alcohol.
 13. A method as defined in claim 11 wherein said mixture comprises between 50 and 85 percent by weight alcohol.
 14. A method as defined in claim 11 wherein said alcohol is a lower alkanol. 